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/*************************************************
* BigInt Assignment Operators Source File *
* (C) 1999-2005 The Botan Project *
*************************************************/
#include <botan/bigint.h>
#include <botan/numthry.h>
#include <botan/mp_core.h>
#include <botan/bit_ops.h>
namespace Botan {
/*************************************************
* Addition Operator *
*************************************************/
BigInt& BigInt::operator+=(const BigInt& n)
{
if((sign() == n.sign()))
{
const u32bit reg_size = std::max(sig_words(), n.sig_words()) + 1;
grow_to(reg_size);
bigint_add2(get_reg(), reg_size-1, n.data(), n.sig_words());
}
else
(*this) = (*this) + n;
return (*this);
}
/*************************************************
* Subtraction Operator *
*************************************************/
BigInt& BigInt::operator-=(const BigInt& n)
{
s32bit relative_size = bigint_cmp(data(), sig_words(),
n.data(), n.sig_words());
if(relative_size == 0)
{
if(sign() == n.sign())
(*this) = 0;
else
(*this) <<= 1;
return (*this);
}
const u32bit reg_size = std::max(sig_words(), n.sig_words()) + 1;
grow_to(reg_size);
if(relative_size == -1)
{
if(sign() == n.sign())
(*this) = (*this) - n;
else
bigint_add2(get_reg(), reg_size-1, n.data(), n.sig_words());
set_sign(n.reverse_sign());
}
if(relative_size == 1)
{
if(sign() == n.sign())
bigint_sub2(get_reg(), sig_words(), n.data(), n.sig_words());
else
bigint_add2(get_reg(), reg_size-1, n.data(), n.sig_words());
}
return (*this);
}
/*************************************************
* Multiplication Operator *
*************************************************/
BigInt& BigInt::operator*=(const BigInt& n)
{
if(is_zero()) return (*this);
if(n.is_zero()) { (*this) = 0; return (*this); }
if(sign() != n.sign())
set_sign(Negative);
else
set_sign(Positive);
const u32bit words = sig_words();
const u32bit n_words = n.sig_words();
if(words == 1 || n_words == 1)
{
grow_to(words + n_words);
if(n_words == 1)
bigint_linmul2(get_reg(), words, n.word_at(0));
else
bigint_linmul3(get_reg(), n.data(), n_words, word_at(0));
return (*this);
}
BigInt z(sign(), size() + n.size());
bigint_mul3(z.get_reg(), z.size(),
data(), size(), words,
n.data(), n.size(), n_words);
(*this) = z;
return (*this);
}
/*************************************************
* Division Operator *
*************************************************/
BigInt& BigInt::operator/=(const BigInt& n)
{
if(n.sig_words() == 1 && power_of_2(n.word_at(0)))
(*this) >>= (n.bits() - 1);
else
(*this) = (*this) / n;
return (*this);
}
/*************************************************
* Modulo Operator *
*************************************************/
BigInt& BigInt::operator%=(const BigInt& mod)
{
return (*this = (*this) % mod);
}
/*************************************************
* Modulo Operator *
*************************************************/
word BigInt::operator%=(word mod)
{
if(mod == 0)
throw BigInt::DivideByZero();
if(power_of_2(mod))
{
word result = (word_at(0) & (mod - 1));
clear();
reg.grow_to(2);
reg[0] = result;
return result;
}
word remainder = 0;
u32bit size = sig_words();
for(u32bit j = size; j > 0; j--)
remainder = bigint_modop(remainder, word_at(j-1), mod);
clear();
reg.grow_to(2);
reg[0] = remainder;
return word_at(0);
}
/*************************************************
* Left Shift Operator *
*************************************************/
BigInt& BigInt::operator<<=(u32bit shift)
{
if(shift == 0) return (*this);
const u32bit shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS;
grow_to(sig_words() + shift_words + (shift_bits ? 1 : 0));
bigint_shl1(get_reg(), sig_words(), shift_words, shift_bits);
return (*this);
}
/*************************************************
* Right Shift Operator *
*************************************************/
BigInt& BigInt::operator>>=(u32bit shift)
{
if(shift == 0) return (*this);
if(bits() <= shift)
{
(*this) = 0;
return (*this);
}
const u32bit shift_words = shift / MP_WORD_BITS,
shift_bits = shift % MP_WORD_BITS;
bigint_shr1(get_reg(), sig_words(), shift_words, shift_bits);
return (*this);
}
}
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